1. Field of the Invention
The present invention relates to an ink jet printing method, a program for carrying out the method and an ink jet printing apparatus, and more specifically, it relates to the method applicable to a system including an ink jet printing apparatus using of three subtractive primary printing agents (ink) and a particular printing agent (ink) having hue different therefrom.
2. Description of the Related Art
A so-called serial scanning type image printing apparatus has been widely used for forming various images, wherein the printing operation is carried out while scanning a printing medium with a printing head which is a printing means. Particularly, such an image printing apparatus belonging to an ink jet system has rapidly prevailed in the market because the resolution or colorization has recently been improved to significantly increase the image quality. While a so-called multi-nozzle head in which ejection openings for ejecting ink, in the form of droplet for example, are disposed at a high density is used in the apparatus of this kind, it has been possible at present to form an image of high resolution by increasing the integrated density of the ejection openings.
Under such a condition, if the number of ink droplets ejected to a unit area of the printing medium in one main scan increases, the ink is liable to blot between ink dots formed on the printing medium. Accordingly, there may be a case in that an image is formed in the same area of the printing medium by a plurality of main scans wherein the printing is carried out so that the respective main scan has a complementary relationship to the other.
By adopting such a printing method, since image data printed by one main scan is properly thinned and all the image data are formed by the plurality of main scans, an amount of ink to be imparted to a unit area of the printing medium by one main scan is decreased, whereby the blot of ink decreases. Since such an effect is enhanced as the number of main scans (the number of passes) is large in the same printing area, it is preferable to increase the number of passes for the purpose of obtaining a high quality image due to the reduction of the blots. When the number of the passes increases however, the total printing time increases so as to decrease to disturb the high speed operation. As described above, the high quality image and the high speed operation are in a trade-off relationship.
To reconcile the high quality image with the high speed operation, there is a method wherein the number of passes is changed in accordance with amounts of ink to be imparted (for example, see Japanese Patent Application Laid-open No. 5-309874 (1993)). More specifically, according to Japanese Patent Application Laid-open No. 5-309874 (1993), the number of passes is changed to be larger or smaller in accordance with amounts of ink to be imparted, because when the amount of ink is increased, the blot of ink is liable to occur, and vice versa.
On the other hand, as the color ink jet printing apparatus has rapidly prevailed at present, further improvement in the quality of color image is desired. Particularly, a clear output image is desired, having a wider color area which could be reproduced by the printing apparatus. In this regard, it is possible to enlarge a color reproduction area in which one of three colors; yellow, magenta and cyan; can be reproduced, by improving the color development characteristic or the condensation of a color material of the printing agent (ink). However, it is difficult to reproduce a clearer color in red, green and blue areas formed by two or more printing agents, especially in a color area having a high chroma, solely by using three colors of yellow, magenta and cyan or four colors adding black thereto, because there is a limit in the color area capable of being reproduced thereby.
To enlarge the color reproduction area, it has been known to use particular color inks such as red, green or blue, in addition to three color inks of subtractive primary colors; yellow, magenta and cyan; or four color inks in which black is further added to the former, each of the particular color inks having a medium hue angle between them in the color space (for example, see Japanese Patent Application Laid-open No. 8-244254 (1996)). In this Japanese Patent Application Laid-open No. 8-244254 (1996), it is contemplated, in addition to the enlargement of the color reproduction area, to reduce the blotting of ink by using the particular color inks. That is, according to Japanese Patent Application Laid-open No. 8-244254 (1996), the area of secondary colors (red, green and blue) is not expressed by the mixture of inks, but expressed by directly using the particular color inks as they are, whereby an amount of ink applied to a unit area is reduced to minimize the ink blotting. In such a manner, when the particular color inks are used, it is possible to reduce the blotting of ink since the ink amount can be decreased when the area of the secondary colors is formed.